--------- Begin forwarded message ----------
From: N4KG
To: k9rz@probe.net
Subject: Re: [TowerTalk] Insulating Guy Wires
On Fri, 18 Jul 1997 22:07:17 +0100 "Bill Jackson" <k9rz@probe.net>
writes:
>Fellow Towertalkers:
>
>I'm looking for information on suggested lengths to break up the guy
>wires
>on an 80 ft tower. I am interested in minimizing the interaction
.............
>73 de Bill
>K9RZ
>
Bill -
I like to use the following arrangements:
----o------------o--------------------------o--------------------------o------------------------
4 12 27 27 27
or 40 etc
----o------------o------------o---------------------------o----------------------------o--------
4 12 12 27 27 or
40 etc
It is important to have an insulator as close to the tower as possible.
This prevents having a near resonance from insulator, through the
tower, and down to another insulator.
(One friend had his insulators 10 ft from the tower, 10 ft below his
tribander. He reported it worked well on 10 and 20, but not on 15.
The top guy wires presented a 21ft span from insulator to insulator
through the tower, making a nice 15M director 1/4 wavelength BELOW
his driven element, sucking signal away from the desired horizon!)
The 12 ft pieces are self resonant around 40 MHz, well above all of
the HF bands and should be virtually invisible. The 27 ft pieces
are self resonant near 18 MHz, and the 40 ft pieces are self resonant
around 12 MHz. Be sure to cut the wires about 1 ft shorter to allow
for the loops at the ends of each guy grip. Another in-between
length for use in l o n g guys is 56 ft. Don't worry about resonance
on the bottom leg, just use whatever is necessary for the last leg.
Be sure to give yourself enough length on the last leg for turnbuckles
and guy wraps. If you extend the wire from the guy wrap above the
turnbuckle, it can be used as a safety with another guy wrap to the
anchor.
I always make a scaled drawing showing the tower, anchor, and
individual guy wires. Then I draw small circles on the guy lines
to indicate insulator positions.
Using Phillystran for the upper portion of the guys is a good idea.
It eliminates the WARC band resonances of the 27 and 40 ft lengths.
73/GL, Tom N4KG
--------- End forwarded message ----------
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